Spray guns and nozzles, especially those used with spray painting systems, atomize the liquid paint by means of atomizing air which enters the nozzle area via a chamber which surrounds a liquid nozzle. The atomizing air exits the chamber via a central aperture located at the end of the chamber. The paint is atomized by the accelerating burst of forward motion of this air as it exits the nozzle via the aperture. The initial conventional pattern of the atomized liquid and air mixture in cross-section is a circle because the exit aperture is circular.
The term "pattern" as used herein describes a cross-section of the atomized cloud of paint droplets in a plane perpendicular to the direction of the spray from the fluid nozzle.
When the compressed air source for a spray painting apparatus utilizes a high volume, low pressure compressor, it is conventional for the air exit nozzle on the spray painting gun to have a central aperture which is considerably larger than the circumscribed liquid nozzle. Therefore, the large amount of air utilized in a conventional nozzle is due to the relative size of the central aperture compared to that of the liquid nozzle. This excess air, air beyond that required to atomize the liquid properly, constitutes an energy waste as well as a pollution problem. The excess air is a pollution problem since the air in a paint system will tend to carry the paint solvent. The more air that is used, the more dilute the solvent, and the more air that must be processed for the removal of solvents.
Therefore, there is a need for an improved spray nozzle which more efficiently utilizes the air that it actually receives from the air source.
The pattern of a spray nozzle is conventionally adjusted by impinging additional air jets on the original circular pattern at a location beyond the outlet aperture. A standard design may include two oppositely directed jets which produce a flat or oval pattern, and if those jets are very powerful they produce a flat fan-shaped spray pattern which is many times wider than it is high. However, in other applications, there are needs for other than such flat or oval patterns, especially when spray painting the reverse sides of objects or spray painting in an out-of-position way and also the traditional problem of painting the inside of angular surfaces.
Another problem with spray guns is that the air from a high volume, low pressure compressor is hot and tends to heat metal parts in the flow path to an extent that hand held spray guns may burn the operator or at least make his hand most uncomfortable.